I took a look at the Piper UWB equipment on 7 line. Few or none of the nodes have a backhaul. Just 120v. They are radio data packet repeaters, not Access Points with their own fiber optic backhaul. I also suspect the next train UWB itself is a rolling radio repeater mesh node. So even though it is NOT AV, if there is a poor to low signal, a train will talk to another train that talks to a repeater node that talks to a backhauled node to a zone controller for CBTC packets. On QBL there are radio nodes ever 600-1000 feet. Almost as bad automatic block track circuits in sheer equipment count, And each legacy radio node must backhaul. Piper equipment just requires 120v, and almost no backhaul cables since it is a mesh network, not a hub spoke wifi system.